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Reaction pathways of iron-sulfide mineral formation; an in situ X-ray diffraction study

Min-Yu Lin, Yen-Hua Chen, Jey-Jau Lee and Hwo-Shuenn Sheu
Reaction pathways of iron-sulfide mineral formation; an in situ X-ray diffraction study
European Journal of Mineralogy (September 2017) 30 (1): 77-84

Abstract

Iron sulfides were synthesized via a co-precipitation method. In addition, synchrotron-radiation experiments were performed under a range of pH and temperature conditions (up to 100 degrees C) to compare the results of in situ and ex situ crystal growth investigation of iron sulfides. In acidic environments, H (sub 2) S acts as an oxidant, oxidizing Fe (super 2+) to Fe (super 3+) and allowing formation of greigite from mackinawite. However, under neutral conditions, due to very low H (sub 2) S concentrations, the oxidant may be S (instead of H (sub 2) S), allowing mackinawite to transform into greigite. Both mackinawite and magnetite were present under alkaline conditions, with possible transitions of Fe (super 2+) +2OH (super -) -->Fe(OH) (sub 2) , followed by 3Fe(OH) (sub 2) -->Fe (sub 3) O (sub 4) +2H (sub 2) O+H (sub 2) . In situ X-ray diffraction results indicate that the mineral transformation rate under acidic conditions is faster than under neutral and alkaline conditions. This means that acid environments can enhance rapid phase transformation of iron sulfides. The results under different experimental conditions suggest that there is a variety of formation pathways for iron-sulfide minerals owing to the presence of different oxidants in different geochemical environments.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 30
Serial Issue: 1
Title: Reaction pathways of iron-sulfide mineral formation; an in situ X-ray diffraction study
Affiliation: National Cheng Kung University, Department of Earth Sciences, Tainan, Taiwan
Pages: 77-84
Published: 20170905
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 60
Accession Number: 2017-085931
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: National Synchrotron Radiation Research Center, TWN, Taiwan
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201745
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